Image-forming optical system, exposure apparatus, and device producing method

ABSTRACT

There is provided a reflective imaging optical system forming an image of a first plane onto a second plane, wherein the numerical aperture with respect to a first direction on the second plane is greater than 1.1 times a numerical aperture with respect to a second direction crossing the first direction on the second plane. The reflecting imaging optical system has an aperture stop defining the numerical aperture on the side of the second plane, and the aperture stop has an elliptic-shaped opening of which size in a major axis direction is greater than 1.1 times that in a minor axis direction. The reflective image-forming optical system is applicable to an exposure apparatus using, for example, EUV light and capable of increasing numerical aperture while enabling optical path separation of light fluxes.

TECHNICAL FIELD

The present invention relates to an imaging optical system, an exposureapparatus, and a method for producing a device. More specifically, thepresent invention relates to a reflective (catoptric) imaging opticalsystem preferably useable for an exposure apparatus which is used toproduce devices such as semiconductors, imaging elements, liquid displaydevices, thin-film magnetic heads, etc. in a lithography step.

BACKGROUND ART

Conventionally, in an exposure apparatus which is used to producesemiconductors, etc., a circuit pattern formed on a mask (reticle) isprojected and transferred onto a photosensitive substrate (for example,a wafer) via a projection optical system. Resist is coated on thephotosensitive substrate, is exposed by being subjected to theprojection exposure via the projection optical system, and thus apattern of the resist (resist pattern) corresponding to a pattern of themask (mask pattern) is obtained. The resolving power (resolution) of theexposure apparatus depends on the wavelength of an exposure light(exposure light beam) and the numerical aperture of the projectionoptical system. Therefore, in order to improve the resolving power ofthe exposure apparatus, it is required to shorten the wavelength of theexposure light and to increase the numerical aperture of the projectionoptical system.

Increasing the numerical aperture of the projection optical system to benot less than a predetermined value is generally difficult in view ofthe optical design. Therefore, it is necessary to shorten the wavelengthof the exposure light. In view of this, attention is directed to an EUVL(Extreme UltraViolet Lithography) technique as a next-generationexposure technique (exposure apparatus) to be used for patterningsemiconductor elements. The EUVL exposure apparatus uses an EUV light(Extreme UltraViolet light or light beam) having a wavelength of, forexample, about 5 nm to about 40 nm. In a case that the EUV light is usedas the exposure light, any usable light-transmissive optical material isabsent. Therefore, in the EUVL exposure apparatus, a reflection typemask is used, and a reflective optical system is used as an illuminationoptical system and a projection optical system (see, for example, PatentLiterature 1).

CITATION LIST Patent Literature

PATENT LITERATURE 1: U.S. Pat. No. 6,452,661

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

As described above, since the resolving power of the projection opticalsystem (imaging optical system) is proportional to the numericalaperture, it is desirable to secure the numerical aperture of theprojection optical system to be as large as possible so as to accuratelytransfer a minute or fine pattern onto a photosensitive substrate.However, the projection optical system which is used in the EUVLexposure apparatus is a reflective optical system, and thus the light isfolded many times, by a plurality of reflecting mirrors, in the opticalpath between the mask and the photosensitive substrate, which in turnmakes it difficult to increase the numerical aperture of the projectionoptical system, due to the purpose of realizing optical path separationfor a plurality of light fluxes travelling in a relatively small ornarrow space between the mask and the photosensitive substrate.

The present invention has been made taking the foregoing problem intoconsideration, an object of which is to provide a reflective imagingoptical system which is applicable, for example, to an exposureapparatus using the EUV light and which is capable of realizingincreased numerical aperture while realizing the optical pathseparation. Further, another object of the present invention is toperform the projection exposure at a high resolution and to secure alarge resolving power by using, for example, the EUV light as theexposure light, with the application of the imaging optical system ofthe present invention to a projection optical system of an exposureapparatus.

Solution to the Problem

In order to solve the problem as described above, according to a firstaspect of the present invention, there is provided a reflective imagingoptical system which forms, on a second plane, an image of a firstplane; characterized in that a numerical aperture, on a side of thesecond plane, with respect to a first direction on the second plane isgreater than 1.1 times a numerical aperture, on the side of the secondplane, with respect to a second direction crossing the first directionon the second plane.

According to a second aspect of the present invention, there is provideda reflective imaging optical system which forms, on a second plane, animage of a first plane; characterized in that a numerical aperture, on aside of the second plane, with respect to a first direction on thesecond plane is greater than 1.5 times a numerical aperture, on the sideof the second plane, with respect to a second direction crossing thefirst direction on the second plane.

According to a third aspect of the present invention, there is provideda reflective imaging optical system which forms, on a second plane, animage of a first plane, characterized by comprising an aperture stopwhich defines a numerical aperture on a side of the second plane;wherein the aperture stop has an elliptic-shaped opening, and a size ofthe elliptic-shaped opening in a major axis direction is greater than1.1 times a size of the elliptic-shaped opening in a minor axisdirection.

According to a fourth aspect of the present invention, there is providedan exposure apparatus characterized by comprising: an illuminationsystem which illuminates, with a light from a light source, apredetermined pattern arranged on the first plane; and the reflectiveimaging optical system of the first, second or third aspect whichprojects the predetermined pattern onto a photosensitive substratearranged on the second plane.

According to a fifth aspect of the present invention, there is provideda method for producing a device, the method characterized by comprisingthe steps of: exposing the photosensitive substrate with thepredetermined pattern by using the exposure apparatus of the fourthaspect; developing the photosensitive substrate to which thepredetermined pattern has been transferred to form a mask layer, havinga shape corresponding to the predetermined pattern, on a surface of thephotosensitive substrate; and processing the surface of thephotosensitive substrate via the mask layer.

Effect of the Invention

In the imaging optical system according to an embodiment of the presentinvention, the elliptic-shaped opening, having the minor axis in afolding direction in which the light flux is folded by a plurality ofreflecting mirrors, is provided on the aperture stop, and the size ofthe major axis of the elliptic-shaped opening is set to be apredetermined time(s) of the size of the minor axis, thereby increasingthe numerical aperture on the image side with respect to the major axisdirection to be a desired size (value), as compared with theconventional technique. Namely, in this embodiment, there is realized areflective imaging optical system which is applicable, for example to anexposure apparatus using the EUV light and which is capable of realizingincreased numerical aperture while realizing the optical path separationof the light flux.

In a case that the imaging optical system of the embodiment is appliedto the exposure apparatus, the EUV light, which has a wavelength of, forexample, 5 nm to 40 nm, can be used as the exposure light. In this case,a pattern of the mask which is to be projected and the photosensitivesubstrate are moved relative to the imaging optical system, therebymaking it possible that the pattern of the mask is projected onto thephotosensitive substrate to expose the photosensitive substratetherewith at a high resolution. As a result, a highly precise device canbe produced under a satisfactory exposure condition by using a scanningtype exposure apparatus having a large resolving power.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a construction of an exposure apparatusaccording to an embodiment of the present invention;

FIG. 2 shows a positional relationship between an optical axis and acircular arc-shaped effective imaging area formed on a wafer;

FIG. 3 schematically shows a construction along an YZ plane of animaging optical system according to a first embodiment;

FIG. 4 schematically shows a construction along a XZ plane of theimaging optical system according to the first embodiment;

FIG. 5 is a first diagram showing the lateral aberration in the firstembodiment;

FIG. 6 is a second diagram showing the lateral aberration in the firstembodiment;

FIG. 7 is a third diagram showing the lateral aberration in the firstembodiment;

FIG. 8 schematically shows a construction along an YZ plane of animaging optical system according to a second embodiment;

FIG. 9 schematically shows a construction along a XZ plane of theimaging optical system according to the second embodiment;

FIG. 10 is a first diagram showing the lateral aberration in the secondembodiment;

FIG. 11 is a second diagram showing the lateral aberration in the secondembodiment;

FIG. 12 is a third diagram showing the lateral aberration in the secondembodiment;

FIG. 13 shows a flow chart concerning an exemplary technique adoptedwhen a semiconductor device is obtained as a microdevice by way ofexample.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be explained based on theaccompanying drawings. FIG. 1 schematically shows a construction of anexposure apparatus according to the embodiment of the present invention.FIG. 2 shows a positional relationship between the optical axis and acircular arc-shaped effective imaging area formed on a wafer. In FIG. 1,the Z axis is defined in the direction of the optical axis AX of areflective imaging optical system (hereinafter referred also simply as“imaging optical system”) 6, i.e., in the normal line direction of anexposure surface (transfer surface) of a wafer 7 provided as aphotosensitive substrate, the Y axis is defined in the directionparallel to the sheet surface of FIG. 1 in the exposure surface of thewafer 7, and the X axis is defined in the direction perpendicular to thesheet surface of FIG. 1 in the exposure surface of the wafer 7.

The exposure apparatus shown in FIG. 1 is provided with, for example, alaser plasma X-ray source as a light source 1 which is provided tosupply the exposure light. It is allowable to use, as the light source1, discharge plasma light sources and other X-ray sources. The light(light beam) radiated from the light source 1 comes into an illuminationoptical system IL, via an optionally arranged wavelength selectionfilter (not shown). The wavelength selection filter has such acharacteristic that only the EUV light having a predetermined wavelength(for example, 13.5 nm), which is included in the lights supplied by thelight source 1, is selectively transmitted through the wavelengthselection filter, and the transmission of the lights having otherwavelengths is shielded or shut off by the wavelength selection filter.The EUV light via (which is allowed to pass through) the wavelengthselection filter is guided to an optical integrator which is constructedof a pair of fly's eye optical systems (fly's eye mirrors) 2 a, 2 b.

The first fly's eye optical system 2 a has a plurality of firstreflecting optical elements which are arranged in juxtaposition or inparallel. The second fly's eye optical system 2 b has a plurality ofsecond reflecting optical elements which are arranged in juxtapositionor in parallel to correspond to the plurality of first reflectingoptical elements of the first fly's eye optical system 2 a.Specifically, the first fly's eye optical system 2 a is constructed, forexample, by arranging a large number of concave mirror elements, havingcircular arc-shaped outer shapes, densely, laterally and longitudinallyin a plane optically conjugate with the first plane. The second fly'seye optical system 2 b is constructed, for example, by arranging a largenumber of concave mirror elements, which have rectangular outer shapes,densely, laterally and longitudinally in the exit pupil plane or a planeoptically conjugate with the exit pupil plane. Reference may be made,for example, to the specification of U.S. Pat. No. 6,452,661 aboutdetailed construction and function of the fly's eye optical systems 2 a,2 b.

Thus, a substantial surface light source, which has a predeterminedshape, is formed in the vicinity of the reflecting surface of the secondfly's eye optical system 2 b. The substantial surface light source isformed at the position of the exit pupil (exit pupil position) of theillumination optical system IL constructed of the pair of fly's eyeoptical systems 2 a, 2 b. The exit pupil position of the illuminationoptical system IL (i.e., the position in the vicinity of the reflectingsurface of the second fly's eye optical system 2 b) is coincident withthe position of the entrance pupil of the imaging optical system(projection optical system) 6 of the far pupil type. The imaging opticalsystem of the far pupil type is an imaging optical system which has theentrance pupil on the side opposite to the optical system with theobject plane intervening therebetween, as will be discussed later. Inthis embodiment, since the shape of the entrance pupil of the projectionoptical system 6 is elliptic-shaped, it is possible, for example, tomake the shape of the exit pupil of the illumination optical system tobe elliptic-shaped. In such a case, it is possible to reduce the lightloss (optical loss).

In other words, the exit pupil of the illumination optical system IL isallowed to have such a shape that the size (dimension) in a thirddirection on the exit pupil plane, at which the exit pupil is located,is smaller than the size (dimension) in a fourth direction crossing thethird direction on the exit pupil plane. In this case, the thirddirection can optically correspond to the first direction (X direction)in which the numerical aperture, of the imaging optical system 6, on theside of the second plane is large; and the fourth direction canoptically correspond to the second direction (Y direction) in which thenumerical aperture, of the imaging optical system 6, on the side of thesecond plane is small. Here, the phrase that “the first direction andthe third direction correspond optically” can be considered that thefirst direction and the third direction are coincident with each otherwhen considering the transformation of projective relationship by theoptical system intervening in a space starting from the exit pupil planeof the illumination optical system IL and arriving at the second plane;and the phrase that “the second direction and the fourth directioncorrespond optically” can be considered that the second direction andthe fourth direction are coincident with each other when considering thetransformation of projective relationship by the optical systemintervening in a space starting from the exit pupil plane of theillumination optical system IL and arriving at the second plane.

Further, the plurality of optical elements of the second fly's eyeoptical system 2 b can be arranged only at a region (area) of which sizeor dimension in the fourth direction is greater than that in the thirddirection. For example, this region may be an elliptic-shaped region.

The light from the substantial surface light source, i.e., the lightexiting or irradiated from the illumination optical system IL isreflected by an oblique incidence mirror 3, and then the light forms acircular arc-shaped illumination area on a reflection type mask 4 via acircular arc-shaped aperture (light-transmitting portion) of a fieldstop (not shown) which is arranged closely to the reflection type mask 4substantially in parallel thereto. In this way, the light source 1 andthe illumination optical system IL (2 a, 2 b) constitute an illuminationsystem which is provided to perform the Koehler illumination for themask 4 provided with a predetermined pattern. No reflecting mirrorhaving any power is arranged in the optical path between the secondfly's eye optical system 2 b and the mask 4.

The mask 4 is held by a mask stage 5 which is movable in the Y directionso that the pattern surface of the mask 4 extends along the XY plane.The movement of the mask stage 5 is measured by a laser interferometerwhich is omitted from the illustration. For example, a circulararc-shaped illumination area, which is symmetrical in relation to the Yaxis, is formed on the mask 4. The light, which comes from theilluminated mask 4, forms an image of the pattern (pattern image) of themask 4 on a wafer 7 as a photosensitive substrate, via the imagingoptical system 6.

That is, as shown in FIG. 2, a circular arc-shaped effective imagingarea ER, which is symmetrical in relation to the Y axis, is formed onthe wafer 7. With reference to FIG. 2, the circular arc-shaped effectiveimaging area ER, which has a length LX in the X direction and which hasa length LY in the Y direction, is formed so that the circulararc-shaped effective imaging area ER is brought in contact with an imagecircle IF in the circular area (image circle) IF which has a radius Y0about the center of the optical axis AX. The circular arc-shapedeffective imaging area ER is a part of the annular or zonal areaprovided about the center of the optical axis AX. The length LY is thewidthwise dimension of the effective imaging area ER provided in thedirection connecting the optical axis and the center of the circulararc-shaped effective imaging area ER.

The wafer 7 is held by a wafer stage 8 which is two-dimensionallymovable in the X direction and the Y direction so that the exposuresurface of the wafer 7 extends along the XY plane. The movement of thewafer stage 8 is measured by a laser interferometer which is omittedfrom the illustration, in the same manner as the mask stage 5. Thus, thescanning exposure (scanning and exposure) is performed while moving themask stage 5 and the wafer stage 8 in the Y direction, i.e., relativelymoving the mask 4 and the wafer 7 in the Y direction with respect to theimaging optical system 6. By doing so, the pattern of the mask 4 istransferred to an exposure area of the wafer 7.

In a case that the projection magnification (transfer magnification) ofthe imaging optical system 6 is ¼, the synchronous scanning is performedby setting the movement velocity of the wafer stage 8 to ¼ of themovement velocity of the mask stage 5. The pattern of the mask 4 issuccessively transferred to the respective exposure areas of the wafer 7by repeating the scanning exposure while two-dimensionally moving thewafer stage 8 in the X direction and the Y direction.

In specified embodiments of the embodiment, as shown in FIGS. 3, 4, 8and 9, the imaging optical system 6 concerning each of specifiedembodiments includes, along the single optical axis AX extending in aform of straight line, a first reflective optical system G1 which formsan intermediate image of the pattern at a position optically conjugatewith the pattern surface of the mask 4, and a second reflective opticalsystem G2 which forms, on the wafer 7, a final reduced image (image ofthe intermediate image) of the pattern of the mask 4. That is, theplane, which is optically conjugate with the pattern surface of the mask4, is formed in the optical path between the first reflective opticalsystem G1 and the second reflective optical system G2.

The first reflective optical system G1 includes a first reflectingmirror M1 which has a concave (concave surface-shaped) reflectingsurface, a second reflecting mirror M2 which has a convex (convexsurface-shaped) reflecting surface, a third reflecting mirror M3 whichhas a convex reflecting surface and a fourth reflecting mirror M4 whichhas a concave reflecting surface as referred to in an order of theincidence of the light. The second reflective optical system G2 includesa fifth reflecting mirror M5 which has a convex reflecting surface, anda sixth reflecting mirror M6 which has a concave reflecting surface asreferred to in an order of the incidence of the light. An aperture stopAS, which has an elliptic-shaped opening elongated in the X direction,is provided on the optical path from the second reflecting mirror M2 andarriving at the third reflecting mirror M3. Any aperture stop is notarranged in the optical path of the imaging optical system 6 other thanthis aperture stop AS, and the numerical aperture of the imaging system6 is determined only with the restriction or limiting of the light fluxby the aperture stop AS.

In the respective specified embodiments, a light from an illuminationarea which is separated from the optical axis AX on the pattern surfaceof the mask 4 (first plane) is successively reflected by theconcave-shaped reflecting surface of the first reflecting mirror M1, theconvex-shaped reflecting surface of the second reflecting mirror M2, theconvex-shaped reflecting surface of the third reflecting mirror M3 andthe concave-shaped reflecting surface of the fourth reflecting mirrorM4, and then the light forms the intermediate image of the mask pattern.The light from the intermediate image formed via the first reflectiveoptical system G1 is successively reflected by the convex-shapedreflecting surface of the fifth reflecting mirror M5 and theconcave-shaped reflecting surface of the sixth reflecting mirror M6, andthen the light forms an reduced image of the mask pattern at aneffective imaging area ER which is separated from the optical axis AX onthe surface of the wafer 7 (second plane).

In the respective specified embodiments, all of the first to sixthreflecting mirrors M1 to M6 are formed to have the reflecting surfaceseach of which is formed to have an aspherical reflecting surfacerotationally symmetric in relation to the optical axis AX. The imagingoptical system 6 concerning each of the specified embodiments is thereflective imaging optical system of the far pupil type which has theentrance pupil, at the position separated by a predetermined distance,on the side opposite to the imaging optical system 6 with the mask 4intervening therebetween. Further, in the respective specifiedembodiments, the imaging optical system 6 is the optical system which istelecentric on the side of the wafer (on the side of the image). Inother words, in the respective specified embodiments, the main lightbeam, which arrives at the respective positions on the image plane ofthe imaging optical system 6, is substantially perpendicular to theimage plane. Owing to this construction, the imaging can be performedsatisfactorily even when irregularities (protrusions and recesses) arepresent on the wafer within the depth of focus of the imaging opticalsystem 6.

First Embodiment

FIG. 3 schematically shows a construction along an YZ plane of theimaging optical system according to the first embodiment; and FIG. 4schematically shows a construction along a XZ plane of the imagingoptical system according to the first embodiment. In TABLE (1) describedbelow shows values of items or elements of the imaging optical systemaccording to the first embodiment. In the columns of the major itemsshown in TABLE (1), λ represents the wavelength of the exposure light, βrepresents the magnitude of the imaging magnification, NAx representsthe numerical aperture on the image side (wafer side) in the Xdirection, NAy represents the numerical aperture on the image side(wafer side) in the Y direction, Y0 represents the radius (maximum imageheight) of the image circle IF on the wafer 7, LX represents the size ordimension in the X direction of the effective imaging area ER, LYrepresents the size or dimension in the Y direction of the effectiveimaging area ER (widthwise dimension of the circular arc-shapedeffective imaging area ER), Dx represents the size or dimension in the Xdirection which is the major axis direction of the elliptic-shapedopening of the aperture stop AS, and Dy represents the size or dimensionin the Y direction which is the minor axis direction of theelliptic-shaped opening of the aperture stop AS.

In TABLE (1), the column for set value of ray tracing and the column forlens data are described in accordance with the format of “Code V” thatis an optical design software produced by ORA (Optical ResearchAssociates). In the column for set value of ray tracing of TABLE (1),“DIM MM” indicates that the dimension is mm; “WL” indicates thewavelength of light (nm). Further, “XOB” indicates X-coordinate (unit:mm), on the wafer 7, of 15 pieces of lights (light beams) used for theray tracing from the image side (wafer side); and “YOB” indicatesY-coordinate (unit: mm), on the wafer 7, of the 15 pieces of lights.

In the column for lens data in TABLE (1), “RDY” indicates the radius ofcurvature of surface (in a case of an aspherical surface, apical radiusof curvature; unit: mm); “THI” indicates a distance from a certainsurface to a next surface, namely spacing between surfaces (unit: mm);“RMD” indicates whether the certain surface is a reflecting surface or arefracting surface. “REFL” means a reflecting surface. “INFINITY” meansthe infinity, and if “RDY” is “INFINITY”, this means that the surface isa flat surface. “OBJ” indicates a surface of the wafer 7 as the imageplane, “STO” indicates a plane of the aperture stop AS, and “IMG”indicates a pattern surface of the mask 4, as the object plane.

Surface No. 1 indicates a virtual surface, Surface No. 2 indicates thereflecting surface of the sixth reflecting mirror M6, Surface No. 3indicates the reflecting surface of the fifth reflecting mirror M5,Surface No′. 4 indicates the reflecting surface of the fourth reflectingmirror M4, Surface No. 5 indicates the reflecting surface of the thirdreflecting mirror M3, Surface No. 7 indicates the reflecting surface ofthe second reflecting mirror M2, and Surface No. 8 indicates thereflecting surface of the first reflecting mirror M1. “ASP” indicatesthat the reflecting surface of each of the reflecting mirrors M1 to M6is an aspherical surface expressed by Expression (a) shown below.

$\begin{matrix}{s = {{\left( {h^{2}/r} \right)/\left\lbrack {1 + \left\lbrack {1 - {\left( {1 + \kappa} \right) \cdot {h^{2}/r^{2}}}} \right\rbrack^{1/2}} \right\rbrack} + {C_{4} \cdot h^{4}} + {C_{6} \cdot h^{6}} + {C_{8} \cdot h^{8}} + {C_{10} \cdot h^{10}} + {C_{12} \cdot h^{12}} + {C_{14} \cdot h^{14}} + {C_{16} \cdot h^{16}} + {C_{18} \cdot h^{18}} + {C_{20} \cdot h^{20}}}} & (a)\end{matrix}$

In Expression (a), “h” is a height (unit: mm) in a directionperpendicular to the optical axis; “s” is a distance (sag amount; unit:mm) along the optical axis from the tangent plane at the apex ofaspherical surface to a position at the height “h” on the asphericalsurface; “r” is the apical radius of curvature (unit: mm); “κ” is theconstant of cone; and “C_(n)” is n-th asphericity. In the column for thelens data in TABLE (1), “κ” is the constant of cone κ; “A” is acoefficient C₄ of h⁴; “B” is a coefficient C₆ of h⁶; “C” is acoefficient C₈ of h⁸; “D” is a coefficient C₁₀ of h¹⁰; “E” is acoefficient C₁₂ of h¹²; “F” is a coefficient C₁₄ of h¹⁴; “G” is acoefficient C₁₆ of h¹⁶; “H” is a coefficient C₁₈ of h¹⁸; and “J” is acoefficient C₂₀ of h²⁰.

Further, “XDE”, “YDE” and “ZDE” show the x-direction component (unit:mm), y-direction component (unit: mm) and z-direction component (unit:mm) of the eccentricity of surface, respectively, in each of thereflecting surfaces (Surface Nos.: 2, 3, 4, 5, 7, 8) of the reflectingmirrors M1 to M6. “ADE”, “BDE” and “CDE” show the θx-direction component(rotational component about the X-axis; unit: degree), θy-directioncomponent (rotational component about the Y-axis; unit: degree) andθz-direction component (rotational component about the Z-axis; unit:degree) of the rotation of the surface, respectively, in each of thereflecting surfaces (Surface Nos.: 2, 3, 4, 5, 7, 8) of the reflectingmirrors M1 to M6. Further, “DAR” means that a coordinate (X, Y, Z) of asurface, located after or downstream of a certain surface, does notchange. Namely, if a certain surface indicated with “DAR” is eccentric,another surface(s) located after the certain surface does not follow thenew, eccentric coordinate; and the eccentricity is unique to the certainsurface indicated with “DAR”. Note that the indication in TABLE (1) isalso same as in TABLE (2) indicated below.

TABLE (1) Major Items: λ = 13.5 nm β = ¼ NAx = 0.4 NAy = 0.2 Y0 = 37 mmLX = 26 mm LY = 2 mm Dx = 84.0838 mm Dy = 41.6781 mm Set Value of RayTracing: DIM MM WL 13.50 XOB 0.00000 0.00000 0.00000 0.00000 0.000006.50000 6.50000 6.50000 6.50000 6.50000 13.00000 13.00000 13.0000013.00000 13.00000 YOB 37.00000 36.50000 36.00000 35.50000 35.0000036.40833 35.90833 35.40833 34.90833 34.40833 34.57082 34.07082 33.5708233.07082 32.57082 Lens Data: RDY THI RMD OBJ: INFINITY 0.000000 1:INFINITY 528.623387 2: −592.28723 −488.623387 REFL ASP: K: 0.000000 A:−.254657E−10 B: −.111703E−15 C: −.366523E−21 D: −.105104E−26 E:−.614569E−32 F: 0.552344E−37 G: −.520745E−42 H: 0.000000E+00 J:0.000000E+00 XDE: 0.000000 YDE: −0.135994 ZDE: 0.000000 DAR ADE:0.002819 BDE: 0.000000 CDE: 0.000000 3: −685.82108 1758.023140 REFL ASP:K: 0.000000 A: −.342613E−08 B: −.598557E−13 C: −.508202E−18 D:0.257521E−21 E: −.629350E−25 F: 0.733153E−29 G: −.349548E−33 H:0.000000E+00 J: 0.000000E+00 XDE: 0.000000 YDE: −0.159098 ZDE: 0.000000DAR ADE: 0.002117 BDE: 0.000000 CDE: 0.000000 4: −1428.35928 −999.904639REFL ASP: K: 0.000000 A: −.224179E−12 B: −.338584E−18 C: −.217996E−23 D:0.151885E−28 E: −.688940E−34 F: 0.153991E−39 G: −.139951E−45 H:0.000000E+00 J: 0.000000E+00 XDE: 0.000000 YDE: 0.174976 ZDE: 0.000000DAR ADE: 0.011492 BDE: 0.000000 CDE: 0.000000 5: −676.50202 265.439672REFL ASP: K: 0.000000 A: 0.128920E−08 B: −.707305E−15 C: 0.189300E−18 D:−.332017E−22 E: 0.330624E−26 F: −.178255E−30 G: 0.404070E−35 H:0.000000E+00 J: 0.000000E+00 XDE: 0.000000 YDE: −0.075707 ZDE: 0.000000DAR ADE: 0.001504 BDE: 0.000000 CDE: 0.000000 STO: INFINITY 464.183715XDE: 0.000000 YDE: 0.014383 ZDE: 0.000000 DAR ADE: 0.000000 BDE:0.000000 CDE: 0.000000 7: −9662.07987 −1139.165307 REFL ASP: K: 0.000000A: 0.168021E−09 B: −.112219E−15 C: 0.887751E−21 D: 0.457673E−25 E:−.216329E−29 F: 0.450161E−34 G: −.378974E−39 H: 0.000000E+00 J:0.000000E+00 XDE: 0.000000 YDE: 0.005654 ZDE: 0.000000 DAR ADE: 0.007150BDE: 0.000000 CDE: 0.000000 8: 2275.61649 1611.423419 REFL ASP: K:0.000000 A: 0.726621E−11 B: 0.832232E−18 C: 0.251018E−22 D: −.243698E−27E: 0.154171E−32 F: −.547826E−38 G: 0.830853E−44 H: 0.000000E+00 J:0.000000E+00 XDE: 0.000000 YDE: −0.029638 ZDE: 0.000000 DAR ADE:0.009792 BDE: 0.000000 CDE: 0.000000 IMG: INFINITY 0.000000 XDE:0.000000 YDE: 0.969601 ZDE: 0.000000 DAR ADE: 0.000000 BDE: 0.000000CDE: 0.000000

FIGS. 5, 6 and 7 are diagrams showing the lateral aberration in thefirst embodiment. In the aberration diagrams, (X, Y) shows thenormalized coordinate system in the effective image area. As apparentfrom the aberration diagrams shown in FIGS. 5-7, it is appreciated thatin the first embodiment, the aberration is satisfactorily corrected withrespect to a EUV light having a wavelength of 13.5 nm although a largeimage-side numerical aperture (NAx=0.4) is secured in the X-direction.Note that the manner of indication in the aberration diagrams of FIGS.5-7 is same also in aberration diagrams shown in FIGS. 10-12 discussedbelow.

Further, when an average value of angles defined between main lightbeams corresponding to respective points in the circular arc-shapedillumination area formed on the mask 4 and a perpendicular line on thefirst plane on which the mask 4 is arrange is “a”, and the maximumnumerical aperture, of the imaging optical system, on a side of the mask4 (side of first plane) is “NAmax”, the following conditional expression(b) is satisfied:

NAmax>sin α  (b)

The average value “a” can be an average of angles each of which isdefined between the perpendicular line and the main light beamcorresponding to one of the respective points, and the average value “a”may be the average of these angles. Note that the respective pointsdescribed above are representative points inside the circular arc-shapedillumination area, and may be, for example, the center point in thecircular arc-shaped illumination area and a most peripheral point in thecircular arc-shaped illumination area.

The conditional expression (b) corresponds to the fact that thenumerical aperture in the X-direction is set to be great with respect tothe average value of the incident angles to the mask 4. Further, theconditional expression (b) corresponds to the fact that an incidentangle of component of incident light in the Y-direction, included in theincident light, becomes great with respect to an incident angle ofcomponent of incident light in the X-direction, due to the purpose ofrealizing the light separation in the imaging optical system.

Note that in a case wherein the main light beam of the incident light isnot perpendicular to a surface of the mask 4 or a surface of the wafer7, the numerical aperture is defined in following manner: namely, when asemicircle having a radius 1 is virtually drawn from the center of anincident light incoming into the surface of the mask 4 or the surface ofthe wafer 7 and an area in which the semicircle and the incoming lightflux are overlapped with each other is projected perpendicularly(orthogonally projected) onto the surface of the mask 4 or the surfaceof the wafer 7, the numerical aperture is defined by a distance betweenthe center of the projected area (for example, circle) and the outercircumference of the projected area (for example, the distance is theradius in a case that the projected area is a circle). On the otherhand, in a case that the project area is an ellipse, the numericalaperture is different between the major and minor axes, and thenumerical aperture is either the major axis or the minor axis.

Second Embodiment

FIG. 8 schematically shows a construction along an YZ plane of theimaging optical system according to the second embodiment; and FIG. 9schematically shows a construction along a XZ plane of the imagingoptical system according to the second embodiment. In TABLE (2)described below shows values of items or elements of the imaging opticalsystem according to the second embodiment.

TABLE (2) Major Items: λ = 13.5 nm β = ¼ NAx = 0.35 NAy = 0.25 Y0 = 41.5mm LX = 26 mm LY = 2 mm Dx = 70.5689 mm Dy = 49.9638 mm Set Value of RayTracing: DIM MM WL 13.50 XOB 0.00000 0.00000 0.00000 0.00000 0.000006.50000 6.50000 6.50000 6.50000 6.50000 13.00000 13.00000 13.0000013.00000 13.00000 YOB 41.50000 41.00000 40.50000 40.00000 39.5000040.97499 40.47499 39.97499 39.47499 38.97499 39.35688 38.85688 38.3568837.85688 37.35688 Lens Data: RDY THI RMD OBJ: INFINITY 0.000000 1:INFINITY 527.112108 2: −586.28043 −487.112108 REFL ASP: K: 0.000000 A:−.236164E−10 B: −.110626E−15 C: −.284530E−21 D: −.544786E−26 E:0.122403E−30 F: −.189106E−35 G: 0.112384E−40 H: 0.000000E+00 J:0.000000E+00 XDE: 0.000000 YDE: 0.023322 ZDE: 0.000000 DAR ADE: 0.001515BDE: 0.000000 CDE: 0.000000 3: −684.71542 1760.000000 REFL ASP: K:0.000000 A: −.396159E−08 B: −.632367E−13 C: −.653539E−18 D: 0.253964E−21E: −.692815E−25 F: 0.989160E−29 G: −.596456E−33 H: 0.000000E+00 J:0.000000E+00 XDE: 0.000000 YDE: 0.009293 ZDE: 0.000000 DAR ADE: 0.000924BDE: 0.000000 CDE: 0.000000 4: −1401.87799 −962.106539 REFL ASP: K:0.000000 A: 0.344061E−13 B: −.777174E−19 C: −.235587E−23 D: 0.104955E−28E: −.323960E−34 F: 0.517487E−40 G: −.351408E−46 H: 0.000000E+00 J:0.000000E+00 XDE: 0.000000 YDE: 0.228380 ZDE: 0.000000 DAR ADE: 0.005863BDE: 0.000000 CDE: 0.000000 5: −682.83983 270.501910 REFL ASP: K:0.000000 A: 0.129775E−08 B: −.134507E−14 C: 0.421784E−19 D: −.278865E−23E: −.509373E−29 F: 0.103118E−31 G: −.381436E−36 H: 0.000000E+00 J:0.000000E+00 XDE: 0.000000 YDE: 0.135445 ZDE: 0.000000 DAR ADE: 0.002567BDE: 0.000000 CDE: 0.000000 STO: INFINITY 405.127751 XDE: 0.000000 YDE:0.236494 ZDE: 0.000000 DAR ADE: 0.000000 BDE: 0.000000 CDE: 0.000000 7:43553.22016 −926.411013 REFL ASP: K: 0.000000 A: 0.275599E−09 B:−.938191E−16 C: 0.115376E−20 D: 0.163736E−24 E: −.956816E−29 F:0.276251E−33 G: −.320812E−38 H: 0.000000E+00 J: 0.000000E+00 XDE:0.000000 YDE: 0.207241 ZDE: 0.000000 DAR ADE: 0.003758 BDE: 0.000000CDE: 0.000000 8: 1921.64574 1412.887892 REFL ASP: K: 0.000000 A:0.122524E−10 B: 0.531596E−17 C: −.102435E−22 D: 0.192287E−27 E:−.152511E−32 F: 0.621001E−38 G: −.102035E−43 H: 0.000000E+00 J:0.000000E+00 XDE: 0.000000 YDE: 0.187309 ZDE: 0.000000 DAR ADE: 0.002261BDE: 0.000000 CDE: 0.000000 IMG: INFINITY 0.000000 XDE: 0.000000 YDE:0.249032 ZDE: 0.000000 DAR ADE: 0.000000 BDE: 0.000000 CDE: 0.000000

FIGS. 10, 11 and 12 are diagrams showing the lateral aberration in thesecond embodiment. As apparent from the aberration diagrams shown inFIGS. 10-12, it is appreciated that in the second embodiment, theaberration is satisfactorily corrected with respect to a EUV lighthaving a wavelength of 13.5 nm although a large image-side numericalaperture (NAx=0.35) is secured in the X-direction.

As apparent from the comparison between FIGS. 3 and 4 and the comparisonbetween FIGS. 8 and 9, an reflective imaging optical system normally hasa design in which the light flux is folded (bent) along a plane (YZplane) including the optical axis AX and the radial direction (Ydirection) passing through the center of the circular arc-shapedeffective imaging area ER on the wafer 7. This is because, in thevicinity of the object plane, it is easy to fold the light flux in anarrow direction in which the circular arc-shaped illumination area onthe mask 4 is narrow (Y direction); and in the vicinity of the imageplane it is easy to fold the light flux in a narrow direction in whichthe circular arc-shaped effective imaging area ER is narrow (Ydirection).

In the present invention, although it is difficult to increase thenumerical aperture with respect to the direction for folding the lightflux (Y direction) in view of the above consideration, the knowledge isobtained that it is relatively easy to realize increase in the numericalaperture with respect to, for example, a direction orthogonal (generallycrossing) the direction for folding the light flux. In each of theembodiments, based on this knowledge, the elliptic-shaped opening isprovided on the aperture stop AS which defines the numerical aperture NAon the image side (on the side of the second plane) and the size Dx inthe major axis direction (X direction) of the opening is made to be apredetermined times greater than the size Dy of the opening in the minoraxis direction (Y direction), thereby securing the image-side numericalaperture NAx in the X-direction to be larger than the image-sidenumerical aperture NAy in the Y-direction and consequently realizing theincrease in the image-side numerical aperture NAx in the X direction.

Specifically, in the first embodiment, the major axis size Dx of theelliptic-shaped opening to be approximately 2.02 times(=84.0838/41.6781) of the minor axis size Dy to thereby increase theimage-side numerical aperture NAx in the X direction to be as much as 2times (=0.4/0.2) the image-side numerical aperture NAy in the Ydirection. Considering that the conventional technique uses the aperturestop having a substantially circular opening and secures an image-sidenumerical aperture which is substantially same in every direction, it isappreciated that the first embodiment increases the size of theimage-side numerical aperture NAx in the X direction to up to be twicethat of the conventional technique.

In the second embodiment, the major axis size Dx of the elliptic-shapedopening to be approximately 1.41 times (=70.5689/49.9638) of the minoraxis size Dy to thereby increase the image-side numerical aperture NAxin the X direction to be as much as 1.4 times (=0.35/0.25) theimage-side numerical aperture NAy in the Y direction. Namely, it isappreciated that the second embodiment increases the size of theimage-side numerical aperture NAx in the X direction to up to be 1.4times that of the conventional technique.

The respective embodiments provide the elliptic-shaped opening on theaperture stop AS in the reflective imaging optical system, the openinghaving the minor axis in the Y direction that is the direction in whichthe light flux is folded, and the size Dx in the major axis direction ofthe opening is made to be approximately 2.02 times or approximately 1.41times the size Dy of the opening in the minor axis direction, therebyincreasing the image-side numerical aperture NAx in the X-direction tobe 2 times or 1.41 times that of the conventional technique. Namely, therespective embodiments realize an imaging optical system which isapplicable, for example, to an exposure apparatus using the EUV lightand which is capable of realizing the increase in numerical aperturewhile realizing the optical path separation for the light flux.

Specifically, in the respective embodiments, it is possible to securethe relatively large image-side numerical aperture in the X direction,with respect to the EUV light having wavelength of 13.5 nm which is 0.4or 0.35 and to secure, on the wafer 7, an effective imaging area whichhas the circular arc-shape and a size of 26 mm×2 mm and in which thevarious aberrations are satisfactorily corrected. Therefore, it ispossible to transfer the pattern of the mask 4 to each of the exposureareas, in the wafer 7, having for example a size of 26 mm×34 mm or 26mm×37 mm by means of scanning exposure with a high resolution of notmore than 0.1 μm.

In the exposure apparatus of the embodiment, a circuit pattern issubjected to the projection exposure by using the imaging optical systemhaving the image-side numerical aperture NAx in the X direction of whichsize is 2 times or 1.4 times that of the image-side numerical apertureNAy in the Y direction. Therefore, with respect to a pattern which is tobe formed by using the theoretical resolution limitation in a layercalled as a critical layer, it is allowable to design the circuitpattern such that the spatial frequency is high (having a small pitch)along the X direction and that the spatial frequency is low (having alarge pitch) along the Y direction.

In the respective embodiments described above, the EUV light having thewavelength of 13.5 nm is used as an example. However, there is nolimitation to this. The present invention is applicable to, for example,to an imaging optical system which uses a EUV light having wavelength ofabout 5 nm to about 40 nm or a light having another appropriatewavelength.

Further, in the respective embodiments, the Y direction is coincidentwith the radial direction passing the center of the circular arc-shapedeffective imaging area ER. However, there is no limitation to this. Theeffects of the present invention can be obtained by making an angledefined by the Y direction and the radial direction passing the centerof the circular arc-shaped effective imaging area ER to be less than 30degrees.

Furthermore, in the respective embodiments, the effective imaging areaformed on the wafer 7 is circular arc-shaped. However, there is nolimitation to this. For example, a rectangular shaped effective imagingarea may also be formed on the wafer 7. In such a case, the effects ofthe present invention can be obtained by making the Y direction tocoincide with a short side direction (narrow side direction) of therectangular shaped effective imaging area. Alternatively, the effects ofthe present invention can be obtained by making an angle defined by theY direction and the narrow side direction of the rectangular shapedeffective imaging area to be less than 30 degrees.

Moreover, the present invention is explained by way of example of thereflective imaging optical system of the far pupil type. However, thereis no limitation to this. The present invention is applicable similarlyto a reflective imaging optical system of the near pupil type. Note thatthe term “reflective imaging optical system of the near pupil type” is areflective imaging optical system having the entrance pupil disposed onthe side of the optical system with the object plane interveningtherebetween.

As described above, it is important in the present invention that, inthe reflective imaging optical system which forms an image of the firstplane on the second plane, the numerical aperture, with respect to thefirst direction on the second plane, on a side of the second plane isgreater than 1.1 times (more preferably 1.5 times) of a numericalaperture, with respect to the second direction crossing the firstdirection, on the second plane, on the side of the second plane.Further, in another point of view, it is important in the presentinvention that, in the reflective imaging optical system which forms animage of the first plane on the second plane, the aperture stop definingthe numerical aperture on the side of the second plane is provided; theaperture stop has an elliptic-shaped opening; and the size of theelliptic-shaped opening in the major axis direction is greater than 1.1times the size of the elliptic-shaped opening in the minor axisdirection.

The exposure apparatus of the embodiment described above is produced byassembling the various subsystems including the respective constitutiveelements as defined in claims so that the predetermined mechanicalaccuracy, electric accuracy and optical accuracy are maintained. Inorder to secure the various accuracies, those performed before and afterthe assembling include the adjustment for achieving the optical accuracyfor the various optical systems, the adjustment for achieving themechanical accuracy for the various mechanical systems, and theadjustment for achieving the electric accuracy for the various electricsystems. The steps of assembling the various subsystems into theexposure apparatus include, for example, the mechanical connection, thewiring connection of the electric circuits, and the piping connection ofthe air pressure circuits in correlation with the various subsystems. Itgoes without saying that the steps of assembling the respectiveindividual subsystems are performed before performing the steps ofassembling the various subsystems into the exposure apparatus. When thesteps of assembling the various subsystems into the exposure apparatusare completed, the overall adjustment is performed to secure the variousaccuracies as the entire exposure apparatus. It is preferable that theexposure apparatus is produced in a clean room in which the temperature,the cleanness, etc. are managed.

Next, an explanation will be made about a device production method usingthe exposure apparatus according to the embodiment described above. FIG.13 shows a flow chart illustrating steps of producing a semiconductordevice. As shown in FIG. 13, in the steps of producing the semiconductordevice, a metal film is vapor-deposited on a wafer W which is to serveas a substrate of the semiconductor device (Step S40); and a photoresistas a photosensitive material is coated on the vapor-deposited metal film(Step S42). Subsequently, a pattern formed on a mask (reticle) M istransferred to each of shot areas on the wafer W by using the exposureapparatus of the embodiment described above (Step S44: exposure step).The wafer W for which the transfer has been completed is developed,i.e., the photoresist, to which the pattern has been transferred, isdeveloped (Step S46: development step). After that, the resist pattern,which is generated on the surface of the wafer W in accordance with StepS46, is used as a mask to perform the processing including, for example,the etching with respect to the surface of the wafer W (Step S48:processing step).

The resist pattern herein refers to the photoresist layer formed withprotrusions and recesses having shapes corresponding to the patterntransferred by the exposure apparatus of the embodiment described above,wherein the recesses penetrate through the photoresist layer. In StepS48, the surface of the wafer W is processed via the resist pattern. Theprocessing, which is performed in Step S48, includes, for example, atleast one of the etching of the surface of the wafer W and the filmformation of a metal film or the like. In Step S44, the exposureapparatus of the embodiment described above transfers the pattern byusing, as the photosensitive substrate, the wafer W coated with thephotoresist.

In the embodiment described above, the laser plasma X-ray light sourceis used as the light source for supplying the EUV light. However, thereis no limitation to this. It is also possible to use, for example, thesynchrotron radiation (SOR) light as the EUV light.

In the embodiment described above, the present invention is applied tothe exposure apparatus having the light source for supplying the EUVlight. However, there is no limitation to this. The present invention isalso applicable to an exposure apparatus having a light source forsupplying a light having any wavelength other than the EUV light.

In the embodiment described above, the present invention is applied tothe imaging optical system provided as the projection optical system ofthe exposure apparatus. However, there is no limitation to this. Ingeneral, the present invention is also applicable similarly orequivalently to any reflective imaging optical system which generallyforms an image of a first plane on a second plane.

Further, in the embodiments, although the present invention is appliedto the reflective imaging optical system of which all the opticalelements are constructed only of the reflecting mirrors, the presentinvention is also applicable to an imaging optical system in which apart of the optical elements is a refractive optical element or adiffractive optical element (reflective type-diffractive optical elementor transmissive type-diffractive optical element).

DESCRIPTION OF REFERENCE NUMERALS

-   -   1: laser plasma X-ray light source    -   2 a, 2 b: fly's eye optical system    -   3: oblique incidence mirror    -   4: mask    -   5: mask stage    -   6: imaging optical system    -   7: wafer    -   8: wafer stage    -   IL: illumination optical system    -   G1, G2: reflective optical system    -   M1 to M6: reflecting mirror

1-25. (canceled)
 26. An exposure apparatus comprising: an illuminationoptical system which has an optical integrator and which illuminates,with an EUV light having a wavelength of 5 nm to 40 nm, a patternarranged on a first plane, the pattern being formed on a reflection typemask; and a projection optical system which has a plurality ofreflecting mirrors and which forms an image of the pattern illuminatedwith the EUV light onto a substrate of which a surface is substantiallyarranged on a second plane, wherein a numerical aperture of theprojection optical system with respect to a first direction on the firstplane is greater than a numerical aperture of the projection opticalsystem with respect to a second direction perpendicular to the firstdirection on the first plane, and the optical integrator of theillumination optical system is arranged apart from the plurality ofreflecting mirrors of the projection optical system in the seconddirection.
 27. The exposure apparatus according to claim 26, wherein theillumination optical system irradiates the first plane with the EUVlight obliquely such that an incident direction of the EUV lightincident on the first plane crosses the first direction.
 28. Theexposure apparatus according to claim 27, wherein the illuminationoptical system irradiate a first region on the first plane with the EUVlight, the first region being separated from an optical axis of theprojection optical system in the second direction.
 29. The exposureapparatus according to claim 28, wherein the EUV light is irradiated ona second region on the second plane via the projection optical system,the second region being separated from the optical axis of theprojection optical system in the second direction, and each of the firstand second regions is circular arc-shaped.
 30. The exposure apparatusaccording to claim 29, wherein the illumination optical system includesa field stop arranged closely to the first plane.
 31. The exposureapparatus according to claim 30, wherein the illumination optical systemincludes a mirror arranged between the first plane and the projectionoptical system, and the EUV light is reflected by the mirror such thatthe reflected EUV light travels toward the first plane and away from theoptical axis of the projection optical system.
 32. The exposureapparatus according to claim 31, wherein a pupil plane of theillumination optical system and a pupil plane of the projection opticalsystem are arranged such that the pupil planes are optically conjugatewith each other, the pupil plane of the illumination optical system hasa size in a third direction and a size in a fourth direction orthogonalto the third direction, the size in the third direction being differentfrom the size in the fourth direction, and the third and fourthdirections optically correspond to the first and second directions,respectively.
 33. The exposure apparatus according to claim 32, whereinthe pupil plane of the illumination optical system has the size in thethird direction which is greater than the size in the fourth direction.34. The exposure apparatus according to claim 33, wherein the pupilplane of the illumination optical system is substantiallyelliptic-shaped.
 35. The exposure apparatus according to claim 30,further comprising: a first stage which is arranged above the projectionoptical system and which holds the mask: a second stage which isarranged below the projection optical system and which holds thesubstrate, and wherein the first and second stages are moved such that ascanning exposure in which each of the mask and the substrate is movedrelative to the EUV light is performed.
 36. The exposure apparatusaccording to claim 35, wherein a numerical aperture of the projectionoptical system with respect to the first direction is greater than 1.1times a numerical aperture of the projection optical system with respectto the second direction.
 37. The exposure apparatus according to claim36, wherein a numerical aperture of the projection optical system withrespect to the first direction is greater than 1.5 times a numericalaperture of the projection optical system with respect to the seconddirection.
 38. The exposure apparatus according to claim 36, wherein thenumerical aperture of the projection optical system with respect to thefirst direction is greatest and the numerical aperture of the projectionoptical system with respect to the second direction is smallest.
 39. Theexposure apparatus according to claim 36, wherein the pupil plane of theprojection optical system is arranged on a side opposite to theprojection optical system with the first plane intervening therebetween.40. A device manufacturing method, comprising: exposing a substrate byusing the exposure apparatus as defined in claim 26; and developing theexposed substrate.
 41. An exposure method, comprising: illuminating apattern arranged on a first plane with an EUV light having a wavelengthof 5 nm to 40 nm via an illumination optical system which has an opticalintegrator, the pattern being formed on a reflection type mask; andforming an image of the pattern illuminated with the EUV light onto asubstrate of which a surface is substantially arranged on a second planevia a projection optical system which has a plurality of reflectingmirrors; wherein a numerical aperture of the projection optical systemwith respect to a first direction on the first plane is greater than anumerical aperture of the projection optical system with respect to asecond direction perpendicular to the first direction on the firstplane, and the optical integrator of the illumination optical system isarranged apart from the plurality of reflecting mirrors of theprojection optical system in the second direction.
 42. The exposuremethod according to claim 41, wherein the EUV light is irradiated ontothe first plane obliquely such that an incident direction of the EUVlight incident on the first plane crosses the first direction.
 43. Theexposure method according to claim 42, wherein the EUV light isirradiate onto a first region, on the first plane, which is separatedfrom an optical axis of the projection optical system in the seconddirection, via the illumination optical system, and irradiated onto asecond region, on the second plane, which is separated from the opticalaxis of the projection optical system in the second direction, via theprojection optical system, and each of the first and second regions iscircular arc-shaped.
 44. The exposure method according to claim 43,wherein a numerical aperture of the projection optical system withrespect to the first direction is greater than 1.1 times a numericalaperture of the projection optical system with respect to the seconddirection.
 45. The exposure method according to claim 44, wherein anumerical aperture of the projection optical system with respect to thefirst direction is greater than 1.5 times a numerical aperture of theprojection optical system with respect to the second direction.
 46. Theexposure method according to claim 44, wherein the numerical aperture ofthe projection optical system with respect to the first direction isgreatest and the numerical aperture of the projection optical systemwith respect to the second direction is smallest.
 47. The exposuremethod according to claim 44, wherein the pupil plane of the projectionoptical system is arranged on a side opposite to the projection opticalsystem with the first plane intervening therebetween.
 48. A devicemanufacturing method, comprising: exposing a substrate by using theexposure method as defined in claim 41; and developing the exposedsubstrate.